(1) Field of the Invention
The present invention is directed to reducing distortion products in the combined outputs of power amplifiers. All the even and many odd order distortion products are suppressed by employing a four phase amplifier. In addition, the distortion products are reduced by 6 dB by employing a feedforward canceler.
(2) Description of Related Art
Distortion products are generated in power amplifiers, particularly due to the transfer characteristics of an active amplifying device. The distortion products are present in the output as harmonics and intermodulation products of fundamental signals which are amplified and distort the amplitude envelope of the fundamental signals injected into the input of the amplifiers. In broadband amplifiers, these distortion products cannot be filtered from the output. In prior art devices, only even order harmonics are suppressed in a push-pull amplifier type device. There is no cancellation of odd order distortion products.
The present invention overcomes the failures of the prior art by obtaining output power that is more linear than the output from prior art devices.